In the oil and gas industry, boilers are used to heat oil emulsion to aide in the removal of water and solids from the oil emulsion. Solids and contaminants from the emulsion collect on the firetube reducing the heat transfer through the tube and increasing the skin temperatures of the firetube, eventually causing material failure.
A firetube is used to heat up a vessel containing an oil and water emulsion and aide the separation of these two components. The initial emulsion may contain polymers, scales, asphalthenes or solids that can collect on the firetube outer surface. The skin temperatures on the firetube are quite high and some contaminants may cook onto the firetube in a hard layer. These cooked on contaminants cannot be removed from the firetube surface using conventional desanding methods. The presence of contaminant buildup causes a reduction of heat transfer from the firetube and can lead to the failure of the firetube through localized overheating. Frequent failures, in the range of every few months, lead to increase treatment costs and undesirable vessel shutdowns to replace damaged firetubes.
GB 190214336 entitled “Improvements in Mechanical Boiler Cleaners” discloses a boiler of the tubular type, and having tubes to clean as part of the object of the invention. Journaled in the ends of the boiler, is a screw-threaded shaft which may be provided at its end extending through, the head or end of the boiler, with a stuffing-box to prevent leakage of steam or water. In referring to FIG. 1, the description states that the outwardly projecting portion of the shaft 22, is preferably formed with a squared end 24, to fit in a similarly-shaped socket 25, on the inner end of a shaft 26, which is journaled in the door 27, of the smoke-chamber 28, of the boiler, and has mounted on its outer portion a pinion 29, to mesh with a gear 30, mounted on a crank-shaft 31, journaled on the door 27. The shaft 22, may be driven by hand, by means of the crank-shaft 31, and gears 29, and 30, or power may be applied by means of a belt (not shown), on a pulley.
GB 191307764 entitled “Improvements in or connected with Apparatus for Scraping Fuel Economisers for Heating Feed Water for Steam Boilers” discloses a class of fuel economisers (known as a horizontal economiser) for heating feed water for steam boilers and in which the tubes are arranged in sections resting on their edges or on the ends of their respective headers in such a way that the tubes have a slight inclination from the inlet to the outlet. The description states that the invention consists of an improved mechanism for actuating the scrapers in an efficient manner without fear of them sticking or tilting. The description states that a driving and reversing mechanism containing a belt driving pulley with spring clutch adjustable to slip in case of obstruction or excessive strain in the scraper gear is positioned at one end of the tubes. The frames carrying the scrapers are provided with wheels which run on or between, rails arranged parallel with the tubes so as to take the weight of the frames and scrapers off the tubes and ensure easy running.
U.S. Pat. No. 7,765,960 entitled “Device for cleaning the fire tubes in a boiler” discloses a device for use when cleaning the heating surface of a tube changer, such as the fire tubes in a boiler, having a scraper member that is fixed to a movement member for moving the scraper member through one fire tube at a time and a guide for positioning the scraper member directly in front of the open end of a fire tube, such that said scraper member can be moved from the guide into the fire tube and conversely from the fire tube into the guide. The description also states that the guide can be moved on a frame transversely with respect to the longitudinal direction of the fire tubes for automatic cleaning of the fire tubes both when in service and out of service.
U.S. Pat. No. 1,849,201 entitled “Pipe cleaning machine” discloses a pipe cleaning machine comprising a frame, means to secure the frame to a pipe so as to secure said pipe against rotation with respect thereto; a pair of feed screws at opposite sides of said frame and revolvable therein; means for revolving said feed screws; a carriage adapted to surround said pipe and to be moved longitudinally thereon by means of said feed screws; means for engaging and for releasing the operative connection between said feed screws and said carriage, and a plurality of scraping knives affixed to said carriage their edges being turned substantially at right angles to the longitudinal axis of the pipe and overlapped so that the entire pipe circumference is touched by knife edges.
U.S. Pat. No. 2,782,436 entitled “Pipe cleaner with tandem scraping heads” discloses an exterior scraper assembly which is adapted to contact with a pipe surface and enter the pitted areas therein to remove foreign matter therefrom. The description teaches an apparatus comprising a pair of cleaning heads connected in tandem by self-adjusting coupling means whereby the front and rear heads are individually free to follow the contour of the pipe when bends are encountered. Each head is provided with a plurality of concave rollers for peripherally aligning the head frames with the axis of the pipe. A plurality of spaced cutter knives are pivotally held on the forward ends of cantilever spring supports which are anchored to the head frames. The description states that the cutter knives carried by each of the heads are arranged in non-tracking or peripherally off-set arrangement so as to have complete coverage of the pipe surface. A secondary spring arm releasably retains the cutter knives at right angles to the axis of the pipe, but the knives are permitted to revolve radially on a hinge means at the end of the cantilever spring support.
U.S. Pat. No. 2,813,285 discloses an apparatus comprising a divided cylindrical head supporting a multiplicity of radially projecting cut with the pipe surface. The apparatus includes spring means for holding the cutter elements yieldingly against the surface of the pipe and for maintaining the cutter means at right angles with respect to the surface of the pipe line. The description states that the cutter unit comprises two rows of offset cutters and is pulled along the line by a truck winch or other drawing power. In tandem with the scraper is a brush-containing pipe cleaner which is attached to the scraping assembly by short lengths of chain. The brush assembly sweeps away any remaining coating or scale to provide a thoroughly cleaned pipe surface.
JP63080195A (Apr. 11, 1988) “Heat Transfer Tube Cleaning Device” discloses a heat transfer tube cleaning device which removes scale, dirt and stain attached to the external surfaces of heat transfer tubes in a heat exchanger by providing an outer frame which reciprocates parallel to a heat transfer tube with a divisional body on which a brush is planted that contacts and slides on the external surfaces of a heat transfer tube.
JP2006138572A (Jun. 1, 2006) entitled “Method for Cleaning Boiler Water Tube” teaches a method for cleaning boiler water tubes that can efficiently clean boiler water tubes without burdening an operator by enabling free movement in boiler water tube banks. It is said that the boiler water tubes are cleaned with a boiler water tube cleaning apparatus comprising a water tube bank traveling cleaning device mounted with rotary brushes and movable axially and vertically in a boiler water tube bank 1 to clean the boiler water tubes, and a tube row direction mobile device movable in a tube row direction as housing the water tube bank traveling cleaning device.
In light of the above prior art, there is still a need for a firetube cleaner adapted to effectively clean the outside of such which combines reliability, relative ease of mounting and allows for simple replacement of scraper fins without the dismantlement of the entire device.